Field of the Invention
The present invention relates to a gas separation apparatus that separates a specific target gas component contained in a gas to be treated, by causing an absorbent to absorb the specific target gas component, and to a packing used therein, and in particular, relates to a gas separation apparatus which brings a gas to be treated such as an exhaust gas into gas-liquid contact with an absorbent and which causes the absorbent to absorb a specific gas component such as carbon dioxide contained in the gas to be treated so as to separate or recover it from the gas to be treated, being useful as a carbon dioxide recovery apparatus, a gas cleaning device to remove a toxic gas, or a separation apparatus to separate a specific gas component from a mixed gas, and to a packing used therein.
Description of the Related Art
Gas separation apparatuses that separate, remove, or recover a specific gas from a gas to be treated such as an exhaust gas containing various kinds of oases, by using gas-liquid contact, have been used in chemical plants or thermal power stations. In a carbon dioxide recovering apparatus, for example, carbon dioxide is separated by absorption that is caused by an absorbent such as an aqueous monoethanolamine solution being brought into gas-liquid contact with a gas containing carbon dioxide, and the carbon dioxide is recovered by heating the absorbent after absorption as well as bringing it into gas-liquid contact to release carbon dioxide into a gas phase. Also in a gas cleaning device to remove a toxic gas component from an exhaust gas or a gas separation apparatus to separate a specific gas component from a mixed gas, a specific gas component is absorbed by an absorbent by using gas-liquid contact. An apparatus for performing gas-liquid contact has a packing for increasing the contact area of the absorbent and the gas, and a specific gas component in the gas is absorbed by bringing the absorbent and the gas into gas-liquid contact on the surface of the packing.
However, in some cases, the absorbent may not flow uniformly on the surface of the packing under the influence of surface tension, and a liquid film of the absorbent flowing on the surface of the packing may be converged to decrease the contact area of the absorbent and the gas. In the case where the gas-liquid contact area decreases, even when the supply flow rate of the absorbent is the same, the absorbent converges on the packing and the velocity of flow increases so that the residence time of the absorbent on the surface of the packing becomes shorter. As a result, a problem is posed that the amount of absorption through contact of the absorbent and the gas is reduced.
Therefore, in a gas-liquid contact device described in Publication Document 1, the gas-liquid contact surface of the packing is configured to be formed of either of a rough surface portion whose average roughness of the center line is 50 μm or more, a porous surface portion having a plurality of perforation holes, or a cancellous object, to increase the gas-liquid contact area.
In a gas-liquid contact device described in Publication Document 2, the gas-liquid contact surface is configured by a material in which a cancellous body is stuck to the surface of a plate, to increase the gas-liquid contact area.
In a gas-liquid contact device described in Publication Document 3, the gas-liquid contact portion is configured by a gas-liquid contact unit in which many three-dimensional knits made of fabric are arrayed vertically or substantially vertically.
In a gas-liquid contact device described in Publication Document 4, a plurality of cancellous bodies which are large enough to cover the cross section of a gas-liquid contact region are disposed and fixed at intervals in the traveling direction of a mixed gas. Publication Document 4 also describes that the cancellous body may be configured by an expanded metal. According to this literature, a part of the injected liquid is scattered after striking the surface of the linear portions forming the mesh of the cancellous body, and the rest part of the injected liquid covers a side face of the linear portions like a thin film and flows down along the side face while it comes into contact with the mixed gas to generate aerosol.